Metabolic and hormonal effects of whole grains of rye, oats and wheat in dog food

Abstract

Inclusion of whole grains in the diet of humans has been shown to improve the postprandial metabolic response and is considered to promote health and prevent certain diseases. Less is known about effects of different whole grains on the metabolic response in dogs. The objective of the present study was to investigate and compare the metabolic and hormonal response in dogs fed extruded diets containing whole grains from rye, oat or wheat, three commonly grown cereals in the Nordic countries. The study was performed in a cross-over design using 18 healthy adult privately-owned dogs. Three extruded experimental diets were produced containing whole grain flour of either rye (RYE), wheat (WHE) or ground rolled oats (OAT) at 25% inclusion level. The diets were nutritionally complete and comparable in terms of protein and metabolizable energy content. Each diet was fed for 4 wk, with blood sampling on the last day of each period (fasting sample followed by post-prandial samples at 20, 40, 60, 120, 180, and 240min). The resulting number of repetitions per diet was: WHE: n=16, OAT: n=17, RYE: n=17. The blood samples were analyzed to determine glucose, insulin, glucagon-like peptide-1 (GLP-1), glucagon, triacylglycerol (TAG) and cholesterol concentrations. There were no main effects of diet on postprandial blood response curves and no effect of interaction of diet and time for any of the variables analyzed. Evaluation of area under the curve (AUC) showed higher total concentration following the OAT than WHE diet for glucose (P=0.035), GLP-1 (P=0.006) as well as TAG (P=0.025). Fasting insulin concentration was higher following RYE compared with both other diets (P=0.005), but there were no differences in insulin AUC between the diets. In the early postprandial phase (0–120min), there was an overall effect of diet on the ratio of insulin to GLP-1 (P=0.042). Post hoc test was not significant, but the WHE diet resulted in a numerically higher value than the other two diets. In conclusion, the postprandial response curves were in general similar between the diets and imply that, in dogs, whole rye or oats may not be more beneficial than whole wheat.